The board said: "Whilst it is not possible to establish a direct link between deaths in custody and low staffing levels, the board does believe that too few staff means reduced vigilance.

"The board's major concern is that for much of the reporting year staffing levels were inadequate, the principal reason for which was the decision taken by the Ministry of Justice some years ago to offer a significant number of experienced officers early retirement and to freeze staff pay."

A spokesman for the Ministry of Justice said: "HMP Chelmsford has already taken significant action to address the concerns raised by the Independent Monitoring Board.

"A dedicated recruitment campaign is under way, and the prison have achieved their benchmark target of 172 prison officers in post.

"There has also been a significant investment in improving safety and reducing violence, including the introduction of body worn cameras, upgrading CCTV and installing additional drug netting in vulnerable areas."